The present invention relates to a display and camera device for a videophone, and a videophone apparatus.
A videophone is a system for bidirectionally transmitting moving pictures and speech of minimum quality over conventional telephone lines. Unlike conventional speech and data communications systems, the videophone allows one party to look the other party in the face and see expressions thereon, and a large amount of information can be transmitted to each party. The videophone is thus expected to be used both for business and at home. In an aging society, talking with one party while looking him or her in the face and seeing the expression thereon will become more and more important for checking his or her condition.
Bidirectional transmission of moving pictures demands a high transfer rate for the conventional telephone lines. However, a moving-picture compression technique having a high compression ratio, which has been improved by digitization of pictures and advances of semiconductor technology, is going to enable a videoconference apparatus to be utilized at average homes over home telephone lines. For this reason, a videoconference system and a stand alone apparatus mounted on a computer, have been developed and are now on sale as products.
In the early stages of a videoconference system, a display device using liquid crystal and a camera using an image pickup device are arranged separately from each other. This arrangement causes a problem of a so-called noncoincidence of lines of sight in which the eyes (line of sight) on the device side do not coincide with those (line of sight) on the display device side. Usually one talks while looking the other party in the face or eyes. A coincidence of lines of sight allows a speaker to speak anytime while looking the other party in the eyes without gazing into the party's eyes for a long time. The speaker determines where to turn his or her eyes according to the importance and contents of conversation. In a noncoincidence of lines of sight, however, the speaker cannot look the party in the eyes. To turn the speaker's gaze on the party's eyes, the speaker has to look at the center of the camera and, in this case, he or she cannot see the party in the display device.
A current videophone used alone or attached to a computer includes a camera and a display provided apart from each other and thus the lines of sight do not coincide. In actuality, an image is not so sharp that the level of eyes cannot be recognized clearly at a 28.8-Kbps communication speed used for the current home telephones, and a user does not care about the noncoincidence of lines of sight; however, this problem becomes serious as the communication speed increases.
Some high-quality videophones which have improved in a coincidence of lines of sight, are already proposed.
For example, Jpn. Pat. Appln. KOKAI Publication No. 63-252084 discloses a videophone in which a beam splitter such as a translucent mirror for reflecting light from a CRT for displaying a picture is provided on an optical path of a camera for taking a picture of a speaker. The beam splitter is so arranged that the optical axis of the reflected light is aligned with that of the camera, and a coincidence of lines of sight is attained.
Since, however, this arrangement necessitates many times as large capacity as that of a conventional television, it is difficult to introduce for home use. A home videophone should not be designed larger than a conventional telephone set.
Jpn. Pat. Appln. KOKAI Publication No. 6-22308 discloses an apparatus in which an optical path extending from a display and an optical path extending toward a camera are deflected by means of a lenticular lens (small-sized prism array) and a light-shield slit. The optical path extending from the display, which goes out of the apparatus after it is deflected, and the optical path extending toward the camera, which is deflected after it enters the apparatus, coincide with each other; thus, a coincidence of lines of sight is achieved.
This apparatus is however difficult to miniaturize since it should be made large to some extent for keeping sufficient characteristics. Probably the characteristics will be degraded due to the light-shield slit.
Recent electronic devices are increased in packing density and their capacities for processing speech and picture signals are improving dramatically. A large scale computer, which was formerly very expensive, is now integrated on a silicon chip 1 cm square and is now much cheaper. It is a small-sized LCD that is the most suitable for the display. Since an LCD not more than 1 inch square has a small substrate, some LCDs are priced very cheaply. On the other hand, a large-sized display is still expensive.
Recently a digital still camera and a digital camcorder have been becoming popular and accordingly a small-sized camera sensor with a lens is decreasing in price. In particular, a CMOS sensor appears in place of a CCD requiring three chips or more. This suggests that a peripheral device, such as an amplifier and an AD converter, is simply integrated and miniaturized.